Traditional indigenous medicines are an etiologic consideration for NELL1-positive membranous nephropathy
Authors: Anila Abraham Kurien, Jansi Prema KS, Patrick D. Walker, Tiffany N. Caza
Journal: Kidney International (2022)

Traditional indigenous medicines (TIM) are founded on ancient historical practice. These medications are obtained over the counter, vary in composition, and contain heavy metals. Their use may not be documented within medical records, and therefore, toxicities of TIM are highly under-recognized. In studies within India and China, TIM have been associated with the development of proteinuric kidney diseases, including minimal change disease and membranous nephropathy (MN), MN being more common.1Kumar M.N. Priyamvada P.S. Chellappan A. et al.Membranous nephropathy associated with indigenous Indian medications containing heavy metals.Kidney Int Rep. 2020; 5: 1510-1514Abstract Full Text Full Text PDF PubMed Scopus (11) Google Scholar, 2Doshi M. Annigeri R.A. Kowdle P.C. et al.Membranous nephropathy due to chronic mercury poisoning from traditional Indian medicines: report of five cases.Clin Kidney J. 2019; 12: 239-244Crossref PubMed Scopus (13) Google Scholar, 3Gao Z. Wu N. Du X. et al.Toxic nephropathy secondary to chronic mercury poisoning: clinical characteristics and outcomes.Kidney Int Rep. 2022; 7: 1189-1197Abstract Full Text Full Text PDF PubMed Scopus (15) Google Scholar The frequency of TIM use in MN is unknown, and the antigenic distribution of this "secondary" association of MN is not previously reported.2Doshi M. Annigeri R.A. Kowdle P.C. et al.Membranous nephropathy due to chronic mercury poisoning from traditional Indian medicines: report of five cases.Clin Kidney J. 2019; 12: 239-244Crossref PubMed Scopus (13) Google Scholar,4Qin A.B. Su T. Wang S.X. et al.Mercury-associated glomerulonephritis: a retrospective study of 35 cases in a single Chinese center.BMC Nephrol. 2019; 20: 228Crossref PubMed Scopus (20) Google Scholar To our knowledge, we present the largest cohort to date of MN associated with TIM use. MN was consecutively diagnosed in 186 patients whose biopsies were received from 92 hospitals throughout India. This cohort was used to evaluate differences between patients with MN taking TIM compared with those without use. The MN cohort included 103 males (55.4%) and 83 females (44.6%). The median age was 41 years (6–80 years). All patients lacked a history of autoimmune disease, 17.7% had diabetes, and 39.2% had hypertension. The majority had nephrotic-range proteinuria (72.6%) and preserved kidney function (81.2% with ≤1.3 mg/dl creatinine). Traditional medications native to India, including Siddha and Ayurveda medicines, were used by 66 patients (35.4%). The median duration of use was 5 months (range, 1–36 months). Patients with MN on TIM had no differences in age, but showed a female predilection (57.6% vs. 37.5%, P = 0.009). Patients on TIM had a higher frequency of diabetes (25.8% vs. 13.3%, P = 0.04). Proteinuria and serum creatinine were similar between the groups (Table 1). Indications for use of TIM varied and included respiratory disorders, skin conditions, arthralgias, hypertension, diabetes, infertility, and cancer treatment.Table 1Clinicopathologic comparisons of patients with MN with or without the use of traditional indigenous medicinesParameterMN on native medicines (n = 66)MN without native medicines (n = 120)Total MN biopsies (n = 186)Native vs. no native medicine, P valueNumber of patients, n (%)66 (35.4)120 (64.5)186 (100)N/AAge, yr (median)4141411.00Sex28 M, 38 F75 M, 45 F103 M, 83 F0.009Serum creatinine1.3 ± 1.41.2 ± 0.91.2 ± 1.10.62Proteinuria (UPCR), g/g6.6 ± 4.16.1 ± 4.26.3 ± 4.20.43Hypertension, n (%)21 (31.8)52 (43.3)73 (39.2)0.16Malignancy1341.00Diabetes, n (%)17 (25.8)16 (13.3)33 (17.7)0.04Antigen typePLA2R-positive69096<0.0001NELL1-positive58664<0.0001PLA2R-negative/NELL1-negative224260.0008MN, membranous nephropathy; N/A, not applicable; NELL1, neural epidermal growth factor-like 1; PLA2R, phospholipase A2 receptor; UPCR, urine protein creatinine ratio. Open table in a new tab MN, membranous nephropathy; N/A, not applicable; NELL1, neural epidermal growth factor-like 1; PLA2R, phospholipase A2 receptor; UPCR, urine protein creatinine ratio. Of patients with MN on TIM, 35 received antiproteinuric therapy with angiotensin-converting enzyme inhibitors or angiotensin receptor blockers, 3 received methylprednisolone, 6 received the Ponticelli regimen of cyclophosphamide followed by methylprednisolone, 2 had rituximab, and 20 were lost to follow-up. Of 46 patients on TIM with follow-up (mean: 111.5 ± 51.0 days, range: 22–222 days), 34 (73.9%) had reduced proteinuria on drug cessation. Thirteen patients (28.2%) achieved partial remission, 21 (45.7%) achieved full remission, 11 (23.9%) had persistent disease, and there was 1 death (2.2%). The majority of patients who went into partial or full remission received only supportive care with discontinuation of TIM and angiotensin-converting enzyme inhibitor /angiotensin receptor blocker therapy (28 patients). Of 11 patients treated with immunosuppression, 6 (54.5%) went into partial or complete remission. Patients on immunosuppression did not have a higher degree of proteinuria than those without immunosuppression (mean proteinuria: 6.9 ± 2.1 g/d vs. 7.7 ± 1.7 g/d, P = 0.92) and did not have improved outcomes. There was 1 death in a patient on immunosuppression who developed sepsis. Immunostaining for the 2 most common targets of MN, phospholipase A2 receptor (PLA2R) and neural epidermal growth factor-like 1 (NELL1), was performed for antigenic subtyping (see Supplementary Methods). Of total MN biopsies, 51.6% were PLA2R-positive, 34.4% were NELL1-positive, and 14.0% were negative for both antigens. Of the 66 patients with MN taking TIM, 57 (87.9%) were NELL1-positive, 6 (9.1%) were PLA2R-positive, and 2 were negative for both antigens (3.0%). In contrast, of patients with MN without TIM use (n = 120), 6 (5.0%) were NELL1-positive, 90 (75.3%) were PLA2R-positive, and 24 (20.0%) were negative for both antigens (Table 1). Representative NELL1 staining is shown in Supplementary Figure S1. Swasa Kalpa, the most common Siddha medicine used, was analyzed for mercury content by mass spectrometry. It contained 132 mg/kg, >200-fold higher than the permissible exposure limit (0.5 mg/kg). Rasagandhi Mezhugu, another Siddha medicine taken by several patients, has been previously reported to have very high mercury content.1Kumar M.N. Priyamvada P.S. Chellappan A. et al.Membranous nephropathy associated with indigenous Indian medications containing heavy metals.Kidney Int Rep. 2020; 5: 1510-1514Abstract Full Text Full Text PDF PubMed Scopus (11) Google Scholar Nine patients taking TIM had serum mercury levels analyzed by mass spectrometry. All had elevated serum mercury and all were NELL1-positive. Given the retrospective observational design, serum samples for mercury analysis were not available for most patients and would be false negative if measured at the time of follow-up due to TIM discontinuation. We also are unable to exclude the possibility of spontaneous remission, as MN is known to spontaneously remit in 32% of patients,5Polanco N. Gutiérrez E. Covarsí A. et al.Spontaneous remission of nephrotic syndrome in idiopathic membranous nephropathy.J Am Soc Nephrol. 2010; 21: 697-704Crossref PubMed Scopus (285) Google Scholar which may be even higher in NELL1-positive patients.6Wang G. Sun L. Dong H. et al.Neural epidermal growth factor-like 1 protein-positive membranous nephropathy in Chinese patients.Clin J Am Soc Nephrol. 2021; 16: 727-735Crossref PubMed Scopus (16) Google Scholar Although a case-control design would have provided stronger evidence for a causal link between use of mercury contaminated TIM and development of MN, other medications known to trigger MN were also identified in observational studies, including nonsteroidal anti-inflammatory drugs7Radford M.G. Holley K.E. Grande J.P. et al.Reversible membranous nephropathy associated with the use of nonsteroidal anti-inflammatory drugs.JAMA. 1996; 276: 466-469Crossref PubMed Google Scholar and lipoic acid.8Spain R.I. Andeen N.K. Gibson P.C. et al.Lipoic acid supplementation associated with neural epidermal growth factor-like 1 (NELL1)-associated membranous nephropathy.Kidney Int. 2021; 100: 1208-1213Abstract Full Text Full Text PDF PubMed Scopus (18) Google Scholar We believe that it is important to consider TIM as an MN association as it is a potentially reversible etiology. We found TIM use in one-third of patients with MN, with the majority being NELL1-positive. Serum mercury levels were increased in all patients who underwent testing (n = 9). The high prevalence of NELL1-positivity in conjunction with the use of TIM raises the possibility of NELL1 being the antigen underlying mercury-associated MN. Mercury nephrotoxicity has been reported to occur in conjunction with TIM from India, Tibet, and China.1Kumar M.N. Priyamvada P.S. Chellappan A. et al.Membranous nephropathy associated with indigenous Indian medications containing heavy metals.Kidney Int Rep. 2020; 5: 1510-1514Abstract Full Text Full Text PDF PubMed Scopus (11) Google Scholar,3Gao Z. Wu N. Du X. et al.Toxic nephropathy secondary to chronic mercury poisoning: clinical characteristics and outcomes.Kidney Int Rep. 2022; 7: 1189-1197Abstract Full Text Full Text PDF PubMed Scopus (15) Google Scholar,4Qin A.B. Su T. Wang S.X. et al.Mercury-associated glomerulonephritis: a retrospective study of 35 cases in a single Chinese center.BMC Nephrol. 2019; 20: 228Crossref PubMed Scopus (20) Google Scholar,9Subbarayappa B.V. Siddha medicine: an overview.Lancet. 1997; 350: 1841-1844Abstract Full Text Full Text PDF PubMed Scopus (65) Google Scholar,S1 In prior reports and case series of MN associated with TIM, there were elevated serum or urine mercury levels, and reversal of disease on drug discontinuation.1Kumar M.N. Priyamvada P.S. Chellappan A. et al.Membranous nephropathy associated with indigenous Indian medications containing heavy metals.Kidney Int Rep. 2020; 5: 1510-1514Abstract Full Text Full Text PDF PubMed Scopus (11) Google Scholar, 2Doshi M. Annigeri R.A. Kowdle P.C. et al.Membranous nephropathy due to chronic mercury poisoning from traditional Indian medicines: report of five cases.Clin Kidney J. 2019; 12: 239-244Crossref PubMed Scopus (13) Google Scholar, 3Gao Z. Wu N. Du X. et al.Toxic nephropathy secondary to chronic mercury poisoning: clinical characteristics and outcomes.Kidney Int Rep. 2022; 7: 1189-1197Abstract Full Text Full Text PDF PubMed Scopus (15) Google Scholar Thus, the association of TIM with the development of MN is not novel; however, it represents the largest series to date. The mechanism through which mercury induces MN is unknown, but there are clues from animal models to explain the etiopathogenesis. Mercury can react with negatively charged glomerular basement membrane components, such as laminin, and transverse the glomerular basement membrane to the subepithelial space.S2 Other cationic substances linked to the development of MN may react similarly, including gold salts, lipoic acid, and cationic bovine serum albumin. NELL1 was previously associated with "secondary" etiologies of MN, including malignancy (33%) and lipoic acid use (14%).8Spain R.I. Andeen N.K. Gibson P.C. et al.Lipoic acid supplementation associated with neural epidermal growth factor-like 1 (NELL1)-associated membranous nephropathy.Kidney Int. 2021; 100: 1208-1213Abstract Full Text Full Text PDF PubMed Scopus (18) Google Scholar,S2,S3 We found that TIM use is an independent association with NELL1 positivity, as only a single patient had concurrent malignancy. The frequency of NELL1-positive MN is higher than reported from the United States, France, and Belgium (71.1% of PLA2R-negative cases, compared with 4%–6% of PLA2R-negative cases in Western countriesS4,S5). This may be attributed to TIM use, as most NELL1-positive patients were taking these drugs. Interestingly, NELL1-positive MN has an identical frequency in China (35%).6Wang G. Sun L. Dong H. et al.Neural epidermal growth factor-like 1 protein-positive membranous nephropathy in Chinese patients.Clin J Am Soc Nephrol. 2021; 16: 727-735Crossref PubMed Scopus (16) Google Scholar TIM use is also common in China, although not investigated as an etiology. NELL1-positive patients were younger in these cohorts from India and China compared with Western cohorts (42–49 vs. 63–67 years),6Wang G. Sun L. Dong H. et al.Neural epidermal growth factor-like 1 protein-positive membranous nephropathy in Chinese patients.Clin J Am Soc Nephrol. 2021; 16: 727-735Crossref PubMed Scopus (16) Google Scholar,S5 which may be due to a higher prevalence of malignancy in older individuals.S4 TIM are widely used; however, the development of MN is rare. This raises the possibility of an underlying susceptibility factor, for which mercury exposure by TIM can serve as a "second hit" to an underlying predisposition. Human NELL1 genetic polymorphisms have been identified in genome-wide association studies,S6 and it is theoretically possible that genetic polymorphisms could underlie susceptibility to mercury-associated MN. In summary, patients with MN in India have a high frequency of TIM use and NELL1-positivity compared with Western cohorts. Given that this represents a reversible process, inquiry about TIM use in patients with MN is highly indicated. All the authors declared no competing interests. This work was supported by the National Institutes of Health grant number 1R41DK130702. Download .docx (1.34 MB) Help with docx files Supplementary File (Word) The authors replyKidney InternationalVol. 103Issue 2PreviewWe found the case reported in the letter by Kaur et al.1 quite interesting. The authors present a patient with phospholipase A2 receptor (PLA2R)–positive membranous nephropathy (MN) in temporal association with complementary medicine containing strontium (Sr2+).1 Several heavy metals have been implicated in MN, most commonly mercury.2,3 Others are (and are not limited to) lead, cadmium, gold salts, silver, and platinum.4 The possibility that Sr2+ is also an exacerbating factor in MN pathogenesis is reasonable. Full-Text PDF Complementary medicine and phospholipase A2 receptor (PLA2R)–related membranous nephropathy—fortuitous or causal?Kidney InternationalVol. 103Issue 2PreviewWe read with interest the article by Kurien et al. highlighting enhanced neural epidermal growth factor-like 1 (NELL-1) expression with complementary and alternative medicine (CAM)–associated membranous nephropathy (MN).1 An association between intake of heavy metals and development of MN has been well described.2,3 Herein, we highlight a novel association of CAM with phospholipase A2 receptor (PLA2R)–related MN. Full-Text PDF